In multi-interface integrated circuit (IC) devices, such as smart card devices that include an ISO-7816 operating mode and a USB operating mode, it is necessary to detect which type of interface is connected to the device. In the case, for example, where the USB interface is not used and the USB host is not connected, the USB pads, (designated D+ and D−), which are associated with the USB host being connected, are left floating on the USB interface side. This floating state of the D+ and D− pads tends to result in an increased power consumption in the IC device and may even render it non-functional. Additionally, software that is embedded in the IC device requires knowledge of the presence of the USB host to activate or deactivate the USB software associated with the IC device, which may cause an additional power drain.
Currently, to perform detection of a USB host, an IC device includes pull-up resistors connected between a power supply and the D+ and D− leads through switches. The USB host, on the other hand, includes pull-down resistors that connect the D+ and D− leads to ground terminals. The pull-down resistors are significantly less resistive than the pull-up resistors. Therefore, if the USB host is present, then D+ and D− are tied to ground through the pull-down resistors, whereas if the USB host is not present, D+ and D− are tied to the power supply via the pull-up resistors. The use of resistors, however, requires a significant amount of physical space to accommodate them, as well as a significant amount of power to drive current through them.